Almost all magnesium metal is made commercially by either of two major processes. When the magnesium-bearing ores--dolomite, magnesite or carnallite--are used, the metal is prepared by thermal reduction of the oxide in the presence of ferrosilicon or carbon. On the other hand, the other major route involves precipitation of the magnesium from undiluted seawater in the hydroxide form, hydrochlorination of the hydroxide back to the chloride form and electrolysis of the molten magnesium chloride.
Despite the widespread use of these processes, recent upward surges in the cost of the high energy requirements of these processes make them subject to replacement in certain instances, e.g. when particular sources of other raw materials are available at low cost and/or when energy requirements may be lessened markedly.
An example of the former situation is MgCl.sub.2 which is produced as a byproduct in the manufacture of titanium metal by reduction of TiCl.sub.4 with magnesium and/or sodium. In one such process, TiCl.sub.4 is reduced with magnesium alone which yields MgCl.sub.2 as a byproduct. In another such process, TiCl.sub.4 is reduced partially with sodium followed by reduction of the subchloride (TiCl.sub.2) with magnesium, which yields a byproduct mixture consisting of MgCl.sub.2 and NaCl. In both cases the byproduct salts are anhydrous and remain so unless they are exposed to air for several minutes.